SCR-type components are components having a structure including a stack of at least four semiconductor layers and/or regions of alternated conductivity types. Such components are, for example, thyristors, triacs, unidirectional or bidirectional Shockley diodes.
FIGS. 1A and 1B respectively are a top view and a cross-section view of an example of a thyristor. FIG. 1B is a cross-section view along broken line B-B of FIG. 1A. These drawings schematically show the thyristor comprising a vertical stack of four semiconductor layers and/or regions 3, 5, 7, and 9 having alternated conductivity types, respectively PNPN.
Heavily-doped N-type region 9 (N+) is formed in P-type doped layer 7. A cathode metallization 11 covers region 9. A gate metallization 13 covers a central portion 14 of layer 7. An anode metallization 15 covers the lower surface of layer 3. Metallizations 11, 13, and 15 respectively form a cathode electrode K, a gate electrode G, and an anode electrode A.
Region 9 is interrupted in areas 17 where cathode metallization 11 comes into contact with layer 7. Areas 17 are currently called emitter short-circuits or emitter short-circuit holes. Such emitter short-circuits 17 are known to improve the dV/dt behavior of the thyristor, thus decreasing the risk of untimely turning-on of the thyristor by voltage peaks.
In FIG. 2, two curves 20 and 22 respectively illustrate the temperature dependence T of turn-on current IGT and of hold current IH in a thyristor of the type described in relation with FIGS. 1A and 1B. The values of the current are indicated as values normalized with respect to their value at 25° C.
Curves 20 and 22 show that the values of currents IH and IGT decrease as temperature T increases. In particular, at −40° C., the value of IGT is two times greater than at 25° C. and, at 140° C., the value of IGT is approximately two times smaller than at 25° C.
In addition to IH and to IGT, the dI/dt characteristic on switching and the dV/dt turn-on characteristic of a thyristor also depend on the operating temperature.
An SCR-type component having characteristics which remain as constant as possible over the entire operating temperature range of the component is needed.